Time delay relay circuit for enginestarting control



y 1950} F. P. SPINELLI ET AL 2,938,127

TIME DELAY RELAY CIRCUIT FOR ENGINE-STARTING CONTROL Filed Nov. 14, 1957 FRANK R JPl/VELL/ Pt'lt' 04s TE/VSC/l/OZD INVENTORS BY a a ATTOP EY United States Patent 2,938,127 TIME DELAY RELAY CIRCUIT FOR ENGINE- STARTING CONTROL Frank P. Spinelli, Teaneck, and Rene Castenschiold, West Caldwell, N.J., assignors to Automatic Switch Co., Florham Park, N.J., a corporation of New York Filed Nov. 14, 1957, Ser. No. 696,360

6 Claims. (Cl. 29036) This invention relates generally to the control of the starting of engines, such as internal combustion engines, and has particular reference to the automatic prevention of starter operation while the engine is running.

A general object of the invention is to provide an improved means by which inadvertent cranking of the engine by its starting device will be prevented during the period following the shutting off of the engine and while the engine is coasting to a stop. It is well known that the cranking of an engine should not be attempted during run of the engine, because of possible damage to the engine or to equipment associated with it. For example, when an attempt is made to crank an engine while it is in operation, stripping of the ring gear, or damage to the cranking motor, or injury from flying metal parts might take place. In addition, there is thelikelihood of injury to nearby personnel.

It is a primary object of this invention to provide a simple but eifective electrical means by which an electrically-operated cranking motor will be rendered inoperable for a period of time after the supply of fuel or current to the engine has been discontinued. The period of inoperability is governed, in part, by the time it takes for the engine to coast to a stop. Hence the arrangement is self-regulating: that is, regardless of the time it may take for the engine to stop, the period of inoperability of the cranking motor is always sufiicient to allow for a complete cessation of rotative movement of the engine before the starter can become effective to restart the engine.

One of the features of the invention lies in the provision of a control circuit having a relay switch so regulated that it will be held open and will not allow closing of the starter circuit during coasting of the engine to a stop, regardless of how long this may take.

The improved starter controlling means involves the association with the engine of a generator adapted to generate a voltage proportional to engine speed, the provision of a control relay which is held open during the application of said voltage to it, and the provision of a special means operable as the engine slows down for delaying the drop-out of the control relay until the engine has come to a complete stop. Briefly stated, the delaying means comprises a condenser shunted across the control relay, and a rectifier arranged between the condenser and the generator.

One way of achieving the foregoing objective and advantages, and such other objects and advantages that may hereafter appear or be pointed out, is illustratively shown in the accompanying diagram.

Referring to the drawing, the reference numeral 1 is applied to a diagrammatically represented engine such as an internal combustion engine. This may be a stationary engine or one provided in an automobile or other vehicle. The cranking or starting motor is indicated at 3, and is coupled to the engine 1 by any conventional means, herein represented as a shaft 2. When the shaft 2 is rotated by the cranking motor 3, it will rotate the crankshaft of the engine 1, thereby to start the engine. The conventional automatically disengaged clutch between the cranking motor and the engine has not been shown, since this is well known per se.

2,938,127 Patented May 24, 1960 The cranking motor 3 is electrically operated from a source of current, such as the battery 6. The circuit includes a lead 5 from the negative side of the battery to the cranking motor 3 and to ground, and a lead 4 from the opposite pole of the battery to the cranking motor. A normally open relay switch 7 is incorporated in the line 4, and it will be apparent that when the switch 7 is open, no current can flow to the motor 3, and when it is closed, current will be supplied through leads 4 and 5 to the cranking motor 3 which will then become effective to crank and start the engine 1.

The relay switch 7 is actuated by a circuit of its own, which includes the coil or solenoid 8 connected to ground by the lead 8a and connected to the positive side of the battery 6 by means of the wiring indicated at 9 and 12. The wire 9 leads to one contact of the switch element 10 of a normally closed control relay. The other contact is connected by wire 25 to the lead 12. The circuit includes an actuating switch 11, which is illustratively depicted as a manually operable push-button switch.

The exciter shown at 19 may be a battery charger or any other appropriate generator which is mechanically connected to and driven by the engine 1 by any suitable drive means illustratively shown as a shaft 18. The generator is adapted to produce a voltage proportional to engine speed.

The generator 19 is in a holding circuit that controls the action of the control relay switch 10. When the generator 19 is in operation during running of the engine 1, it supplies current through leads 20 and 21 to energize the relay coil or solenoid 24 by means of which switch 10 is actuated.

The arrangement preferably includes a normally ineffective engine-stopping circuit which has in it an actuating switch 16 and a normally open switch 14. The latter is preferably mechanically coupled to the part 10 to operate with it when the coil 24 is energized and de-energized.

It will be noted that while the engine 1 is in operation and the generator 19 is supplying current to energize the coil 24, the coil 24 is efiective to close switch 14 and open switch 10. Switch 14 has one side connected by the leads 13 and 12 to the positive side of the battery 6, while the other side of the switch 14 connects to wire 15 which extends through actuating switch 16 to a pumpclosing solenoid 17 (marked P.C.S.). This solenoid is efiective to shut off the supply of fuel to the engine. Any equivalent engine-stopping instrumentality may be used.

In the holding circuit, a condenser 23 is shunted across the control relay. At 22 is shown a rectifier located in a line 20 between the generator '19 and the point of connection of the condenser 23. The rectifier 22 makes it possible to actuate the relay coil 24 by both alternating and direct current, and at the same time it performs the important function of preventing the condenser 23 from discharging through the generator 19. Under certain circumstances, e.g., with higher exciter voltages, two or more rectifiers may be arranged in series.

From-the foregoing, the operation of the improved starter controlling means will be readily understood. As depicted in the drawing, the elements are all shown in the positions assumed by them when the engine is not running and all coils are de-energized. To start the engine, the actuator switch 11 is closed (either manually or through a remote control), and the current flowing from the battery 6 through leads 12, 25', and 9 will energize the starter relay 8. This will cause switch 7 to close and thereby set the cranking motor 3 into operation. When the engine starts, it will set the exciter or generator 19 into operation, whereby current is supplied to the relay coil 24. This become effective to close switch 14 and to open switch 10. While the exciter 19 is supplying current to energize the coil 24 it is also charging the condenser 23. So long as the enggine 1 is running, and the switch is open, the cranking motor will be inoperable and cannot duringthis time be started by operation of the actuating switch 11. The switch 10 will remain open, of course, as long as an adequate current continues to be supplied to the relay coil 24.

Switch '16, which can be remotely located and can 'be either manually operated or automatic, is employed for shutting ofi'the engine. 'It is efiective for this purpose so long as switch 14 is closed, and this is the case whenever the engine is running. When the switch 16 "is closed, current is supplied through leads 12, 13, closed switch 14,

and wiretothe'pump control solenoid or other enginestopping device 17. I

Since it is desirable that the engine shall not be started by operation of the actuating switch 11 during the coasting of the engine i.e., during that period in which the engine is' turning over solely by inertia after the fuel supply or other necessary factor has been shut off, it is important that switch 10 shall assuredly remain open during this entire coasting period of the engine and until the engine comes to a full stop. This is achieved by the holding circuit, more particularly by the rectifier 22 and the condenser 23. As the engine starts to slow down, the current supply from the generator 19'will be correspondingly reduced because the voltage output of the generator falls at a rate proportional to engine speed. At the same time, the condenser 23 discharges through the relay coil at a rate dependent on this changing voltage. By proper selection of condenser and relay coil, the discharge of the condenser can be caused to prevent the relay from dropping out until a predetermined fixed time (say, four or five seconds) after the engine has reached a complete standstill. The time delay thus'varies in accordance with the formula where TD is the drop-out delay of the relay, ST is the stopping or coasting time of the engine, and P is the fixed delay period. The period P can be selectively varied by choosing different values of capacitance or changing the characteristics of the relay coil or frame. (Theoretically, the fixed delay period P decreases slightly for longer engine shutdown periods but this change is insignificant in comparison to the actual shutdown periods of conventional internal combustion engines.)

From the foregoing, it will be observed that the arrangement described is self-regulating, and that regardles of the time required by the engine to coast to a stop it is impossible to actuate the cranking motor during this time and during a fixed predeterminable period thereafter. Thus undesired operation of the cranking motor at any time while the engine is turning over, either under power or under inertia, will be prevented and possible damage to the engine or its associated parts avoided.

While the invention is not restricted to the control of engines of any particular kind or magnitude, nor to any specific degree of additional time delay P in the release of the control relay, it may be pointed out by way of example that a typical installation of the character described has been satisfactorily employed to control a 90 horsepower l200 r.p.m. stationary internal combustion engine, as follows: The exciter employed was a 60-volt direct current generator. The condenser was an electrolytic one and had a capacity of 80 microfarads and a working voltage of 150 volts D.C. The control relay coil had 21,600 turns of No. 39 enamel wire and a resistance of 6,500 ohms. The rectifier was rated at 130 volts (maximum) AC. input, and 0.075 ampere (maximum) D.C. output. The relay drop-out time delay (P), beyond the 7 complete stoppage of the engine, was about five seconds.

It is to be understood that these and "other details herein set forth are given merely by way of example, and

are to be construed as being illustrative only. Changes in these details may be made'by those skilled in the art without necessarily departing from the spirit and scope of the invention as expressed in the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A starter controlling means'for an engine, comprising a cranking'motor, an electric circuit therefor having a normally open relay in it, a circuit for said relay including an actuating switch'and also a normally closed control relay switch, a control relay for opening said switch, a holding circuit for saidcontrol relay, a generator in said holding circuit driven by said engine and constructed and arranged to generate a voltage proportional to engine speed, said voltage serving to energize said control relay and holdsaid switch open as long as the engine is running, and means operable as the engine slows down for delaying the drop-out of said control relay until the engine comes to a'complete stop.

2. A controlling means as defined in claim 1, said delaying means comprising a condenser shunted across the control relay, and a'rectifier in the holding circuit between said condenser and the generator.

3. A starter controlling means for an engine, comprising a cranking motor, an electric circuit therefor having a normally open relay in-it, a circuit for said relay including an actuating switch and also a normally closed control relay switch, a control relay foropening said switch, a holding circuit for said control relay, a generator in said holding'circuit d'rivenby said engine and'constructedand arranged to generate a voltage proportional to engine speed, said voltage s'ervi'ngto energize said control "relay and hold said switch open as long as the engine is running, means operable as the engine slows down for delaying the drop-out of said control relay until the engine comes'to a complete stop, and an engine stopping circuit including an actuating switch and a normally open switch, the movable part of said last-named switch being mechanically connected to the movable part of said control relay, whereby the energization of said control relay when the engine is running serves simultaneously to open said control relay and to close the switch in the engine stopping circuit, and vice versa.

4. The combination'with' an engine, of an engine stopping circuit comprising an actuating switch and a'normally open control relay switch, a control'relay for closing said switch, a holding circuit for said control relay, a generator in said holding circuit driven by said' en'gine anal constructed and arranged to generate a voltage proportional to engine speed, said voltage serving to energize said control relay and hold said switch closed as long as References Cited in the file of this patent UNITED STATES PATENTS Re. 15,258 Ernest Jan. 3, l922 1,415,159 Daggett May 9, 1922 1,606,043 Radley Nov. 9, 1926 1,736,865 Starr Nov. 26, 1929 2,603,756 Puttick July 15, 1932 2,144,786 Baer et a1. Jan. 24, 1939 2,249,488 Nickle July 15, 1941 2,282,182 Gulliksen May 5, 1942 

